Dynamics of Wind Turbine Blades Using a Geometrically-Exact Beam Formulation

Abstract

Abstract. On wind energy context, the blades of horizontal axes wind turbines have, in their majority, a closed multicellular thin-walled cross section, which varies along the blade length due to aerodynamic requirements. If one wants to analyze the structural behavior of such blades, a dynamic model is necessary. Such models are desirable, since it is important the development of lighter and more flexible wind turbine designs. The desirable results of the models include evaluating the possible large deflections along time, the internal loads along the blade length and natural frequencies experimented by the structure. Moreover, one can address the magnitude and frequency of the reactions lying at the top of the turbine tower structure, due to the action of the blades. In order to model the blades with a small number of degrees of freedom, geometrically-exact beam elements are employed. The equivalent properties to be input in the model, however, are not straightforward to be obtained. This is one of the goals of the present work. A pre-processor was developed to evaluate the cross sections properties of a wind turbine blade. It calculates all the necessary input data to represent the blade as an equivalent beam and, generates an input file with data of the model to be solved in the geometrically-exact GIRAFFE dynamic simulator. Since dealing with multicellular thin-walled cross section, it is important to evaluate the centroid, the barycenter, the shear center, the inertia properties, and the equivalent specific mass. All these properties may vary along the blade length. It is possible to manipulate the blade profile, changing the number of cells, thickness, materials involved, shape of the external shell and webs positioning. The developed pre-processor, together with the dynamic simulator, can be used to predict large displacements in a dynamic simulation of wind turbines. 4503

Uma formulação de contato C¹ baseada em splines: aplicações têxteis

“…Figure 78 presents normal contact forces obtained from the biaxial tension simulation in [1] and from the spline-based contact formulation. It is possible to note that a single contact force is present in each yarn's contact region instead of multiple forces in [84]. In Experimental" in black from [7], "Surface" in blue from [1], and "Spline" in red from the spline-based contact formulation.…”